You are deploying several CloudFormation templates. Whilst deploying the templates, you are getting the below error.
Error
Type Sender
Code
Throttling
Message Rate exceeded
Which of the following can be done to resolve the issue?

Answer options:

A.Add a pause in the CloudFormation templates.
B.Add an exponential backoff between the calls to the createStack API.
C.Use a large instance from where the CloudFormation template is being deployed.
D.Combine the stacks into one template and deploy the stack.

Correct Answer: B
The error is happening because the create stack API is creating too many resources at the same time. You can add some delayed requests using a concept called exponential backoff.
Option A is incorrect since you cannot add a pause. You can add wait or dependency conditions in CloudFormtion.
Option C is incorrect because using a large instance will not help because this is an issue with the number of requests being fired against CloudFormation.
Option D is incorrect because using one larger template will make the situation worse.
For more information on exponential backoff, please visit the following URLs-
https://forums.aws.amazon.com/thread.jspa?threadID=100414
https://docs.aws.amazon.com/general/latest/gr/api-retries.html 
https://aws.amazon.com/blogs/messaging-and-targeting/how-to-handle-a-throttling-maximum-sending-rate-exceeded-error/